 Physics Core/AP 1 and 2

#### Course Materials are always under revision! Weblecture content may change anytime prior to two weeks before scheduled chat session for content. Homework

# Physics 19: 5-8 RC Circuits

## Homework

### Reading Preparation

Text Reading: Giancoli, Physics - Principles with Applications, Chapter 19: Sections 5 to 8

##### Study Points
• 19.5 Capacitance in parallel and series circuits adds up exactly the reverse of resistance. In a series of two capacitors, you add 1/C1 + 1/C2 = 1/Ctotal. In a parallel circuit, you simply add capacitances: C1 + C2 = Ctotal.
• 19.6 The voltage of an RC circuit follows the rule V across the capacitor = emf * (1 - e-t/RC) where e is the base for natural logarithms. This type of circuit has to be analyzed using calculus (and in fact, can be set up to be analogous to many differential equations). The value t = RC is the time it takes to charge a capacitor to 63% of its maximum.
• 19.7 Electrical shocks can burn tissue or disrupt the normal electrical impulses used to trigger heartbeat or brain functions. Always follow safe practices in working with electrical circuits.
• 19.8 Ammeters measure current, voltmeters measure potential difference, multimeters measure both, and ohmmeters measure resistance.

### Key Equations

• Capacitance in a Series Circuit:
• Capacitance in a Parallel Circuit:

### Web Lecture

Read the following weblecture before chat: DC Circuits: Capacitance and Resistance

### Study Activity

Use the capacitance lab to experiment with plate charges.'

• What happens to the capacitance and the electric field if you vary the voltage on the battery?
• What happens if you vary the plate separation?
• What happens if you vary the plate area?

Physics simulation Java Applets are the product of the PHET Interactive Simulations project at the University of Colorado, Boulder.

Optional Website:

Please return to the Learn Physics Today! site, to look at the Unit 3, chapter 15 lecture on the more exotic aspects of circuits.

### Chat Preparation Activities

• Forum question: The Moodle forum for the session will assign a specific study question for you to prepare for chat. You need to read this question and post your answer before chat starts for this session.
• Mastery Exercise: The Moodle Mastery exercise for the chapter will contain sections related to our chat topic. Try to complete these before the chat starts, so that you can ask questions.

### Chapter Quiz

• Required: Complete the Mastery exercise with a passing score of 85% or better.
• Go to the Moodle and take the quiz for this chat session to see how much you already know about astronomy!

### Lab Work

If you want lab credit for this course, you must complete at least 12 labs (honors course) or 18 labs (AP students). One or more lab exercises are posted for each chapter as part of the homework assignment. We will be reviewing lab work at regular intervals, so do not get behind!